It is known to line the lip of a shaft seal with a liner of material having a low coefficient of friction (hereinafter referred to as a low friction material). However, problems are encountered when the diameter of the sealing lip is less than about 0.5". This situtation usually requires pre-forming the polytetrafluoroethylene (or other low-friction material) disc prior to molding, thus increasing the costs involved. Problems are also involved when the seal cross-section (the radial dimension between the seal inside and outside radius, i.e. dimension "A" in FIG. 1) is narrow (hereby defined as being less than approximately 0.125"). In this case, there is not sufficient room available to use the normal metal shell and polytetrafluoroethylene liner in the seal without minimizing the rubber bonding area with respect to the shell and the liner to such a small amount that it could cause seal failure. Therefore, the shell must be omitted, causing a problem with seal retention in the bore and proper square seal alignment (especially on through bores i.e., bores such as bore 12 in FIG. 2 without a shoulder abutting the seal).
It is an object of the present invention to provide a seal, a method for making a seal, and a method for maintaining seal alignment that overcome the above-mentioned problems in the prior art.
It is another object of this invention to provide a seal consisting solely of an elastomeric body and a low friction liner (i.e. a seal with no metal shell), wherein the liner has a radial flange extending radially out beyond the outside diameter of the elastomeric body for locating, retaining, and aligning the seal in a housing bore.
It is another object of this invention to provide a method for making a seal using a single sheet of low friction material in a multi-cavity mold to reduce expensive manufacturing operations and to improve material handling.